Okay, so about 3.5 to 3.2 billion years ago, the cyclic pathway of photosynthesis had evolved in certain anaerobic bacteria... 2 billion years ago, geological records showed the presence of oxidized sediments indicating that by the action of living organisms, the atmosphere was being transformed into a highly oxidizing state from a reducing one.

These first organisms were prokaryotic and from these protobionts came prokaryotic organisms called methanogens.

A second line rose from these protobionts--> other bacteria free living and parasitic to the blue or green algae (or cyanobacteria)

So once all of this happened, and the prokaryotes had risen on earth, these prokaryotes gave rise to eukaryotes. The eukaryotes had only been around for seven hundred million years and the first three billion years it was all about the prokaryotes.

Eukaryotes were thought to have risen from certain prokaryotic cells living as endosymbionts in other cells. At this time, current organelles such as mitochondria and chloroplasts were probably once organisms in their own right. Ancient mitochondria or chloroplasts began living inside other organisms and eventually formed a new association which became a new type of organism (eukaryotes?).

So the process continues, as current organisms combine with each other to form new organisms. And we humans are known as eukaryotic organisms, and we tend to look at prokaryotic cells and eukaryotic cells as separate items, but if it wasn't for the older prokaryotes, we could not be in existence today. If somehow someone went back in time and stopped the process of eukaryotes rising from prokaryotes, the world would look a little different today me thinks.